Backhoe



April 9, 1968 L B LONG ET AL 3,376,984

BACKHOE Filed NOV. 16, 1966 2 Sheets-Sheet 1 April 9, 1968 E, 5, LONG ET AL 3,376,984

BACKHOE Filed Nov. 16, 1966 2 Sheefs-Shee 2 a 5%;mQ/'r .07- roe/VIKS United States Patent 3,376,984 BACKHOE Elton B. Long, Burlington, and John F. Shumaker, Mount Pleasant, Iowa, assignors to J. I. Case Company, a corporation of Wisconsin Filed Nov. 16, 1966, Ser. No. 594,813 7 Claims. (Cl. 214-138) ABSTRACT OF THE DISCLGSURE A backhoe arrangement is disclosed wherein overcenter forward movement of the boom and boom cylinder provides a transport configuration for the backhoe wherein the center of gravity is substantially closer to the rear of the vehicle. A swing tower of cradle form is attached at the rear of a vehicle and serves as a support that embraces the pivotally mounted boom, with a pair of outboard mounted boom cylinders being pivoted on the swing tower to flank the boom in a clearance relationship that permits the boom to assume a substantially vertically directed neutral intermediate position. The boom cylinders are operable to control the boom to swing to either side of neutral position.

possible to the rear of the mounting vehicle. However,

the main center of gravity is still so far to the rear of the vehicle, typically 42.5 inches to the rear of the mounting pivots for the swing tower, that mechanical balance relationships are insufiiciently stable and handling is unduly dilficult, even during normal use as a loader.

In accordance with the present invention, a backhoe arrangement is provided wherein the center of gravity for the backhoe is substantially closer to the rear of the vehicle. The present backhoe is arranged to accommodate an overcenter movement of the boom cylinder when the boom is swung to transport position. In the transport position, the backhoe has a generally vertically and slightly forwardly extending boom-held locked in position by the boom cylinder which has gone overcenter.

In the disclosed embodiment, a swing tower of cradle form embraces the boom and a pair of outboard mounted boom cylinders flank the boom and connect to the swing tower in a fashion to accommodate the required forward travel of the boom relative to the boom cylinders. The ability of the boom to assume a more forwardly inclined relationship effects an improvement in the position of the center of gravity of as much as 50 percent to provide better balance and handling and to limit the backhoe tail swing required in close quarter operations.

Other features and advantages of the invention will be apparent from the following description and claims, and are illustrated in the accompanying drawings which show an illustrative embodiment of the present invention.

In the accompanying drawings forming a part of the specification, and in which like numerals are employed to designate like parts throughout the same,

FIGURE 1 is a side elevational view of the backhoe of this invention representing the parts in an intermediate 3,376,984 Patented Apr. 9, 1968 position which corresponds to the normal transport position of the prior art arrangement;

FIGURE 2 is a side elevational view of the present backhoe showing the parts in an intermediate position wherein the boom cylinder is aligned with the pivot axis of the boom;

FIGURE 3 is a side elevational view of the present backhoe showing the parts in maximum transport position wherein the boom cylinder is overcenter relative to the boom to effect a knee lock action;

FIGURE 4 is an enlarged fragmentary perspective view of the swing tower and boom mounting arrangement utilized in the present backhoe; and

FIGURE 5 is a fragmentary plan view, partly in section, further showing the swing tower and boom mounting.

Referring now to the drawings, a backhoe arrangement designated generally at 10 is shown pivotally mounted upon the rear of a tractor, illustrated only fragmentally as indicated at T.

The backhoe assembly includes a support attachment in the form "of a swing tower 11 pivotally mounted to rearwardly projecting tractor mounting brackets 12 by means of upper and lower swivel pins 13, 14 which collectively define a common vertical axis. A swing cylinder 11H is shown forpositioning the swing tower.

As is conventional, the swing tower 11 carries a bottom horizontal pivot shaft 15 mounting a boom 16 and upper horizontal pivot shafts 17 mounting boom cylinders 18. Each boom cylinder 18 is of a double-acting type and has a single-ended piston rod 19 pivotally connected upon a pivot shaft 20 located adjacent the free end of the boom.

A dipper 21 is mounted on a pivot shaft 22 carried at the free end of the boom to define a pivot axis for the dipper at a location intermediate along its length, but substantially closer to the boom end than to the bucket end of the dipper. The dipper 21 includes a rigid attachment plate ZIP constituting its boom end and receiving the pivot shaft 22. A single dipper cylinder 23, also of a double-acting type, is mounted on a pivot shaft 24 carried on the boom adjacent its lower end. The dipper cylinder 23 has a single-ended piston rod 25 pivotally connected on a pivot shaft 26 carried at the end corner of the attachment plate 21?.

A bucket 26 is pivoted to the free end of the dipper in the conventional way. A pair of drive links 27 and 28, respectively, are pivoted to the dipper 21 and to the bucket 26 and are interconnected by a floating knee shaft 29. A bucket cylinder 30 of a double-acting type is mounted on a pivot shaft 31 carried on an upstanding corner of the dipper attachment plate 21F and has a single-ended piston rod 32 pivotally connected to the knee shaft 29.

Referring now to FIGURE 1, the backhoe is shown in an intermediate position, which corresponds to the normal transport position for the case of the prior art structures. In this configuration, the boom extends generally vertically and rearwardly and the center of gravity of the backhoe parts is located along the vertical line indicated by the arrow A, which is a typical prior art backhoe is 42.5 inches to the rear of the swivel pins 13 and 14. The boom cylinders 18 act at a moment arm as indicated at M and hydraulic pressure must be applied to the rod end of the boom cylinders 18 to restrain the parts. In any event, the rearward location of the backhoe center of gravity alfects the balance of the unit and makes handling more diflicult, both during transport and in normal use.

The present backhoe arrangement has a normal transport position as shown in FIGURE 3, wherein the boom extends generally vertically and slightly forwardly, and the center of gravity is located along the vertical line indicated by the arrow B, which typically is 20.0 inches to the rear of the swivel pins 13 and 14. The boom cylinders 18 act at a moment arm M, and application of hydraulic pressure to the piston end of the boom cylinders effects a knee lock joint to hold the parts in the FIGURE 3 position. Balance and handling of the unit is greatly improved as the effective center of gravity has been shifted forwardly by more than 50 percent.

In the disclosed embodiment, the swing tower 11 is a cradle-like structure generally U-shaped in plan outline and including a vertical forward wall 11F and a pair of rearwardly projecting sidewalls 11S defining a channel space 11C in which the boom 16 is nestable.

The lower rearward extremities of the sidewalls serve as mounting sockets for the boom pivot shaft and the upper rearward extremities of the sidewalls serve as mounting sockets for the boom cylinder pivot shafts 17. The pivot shafts are outboard to locate the boom cylinders 18 outboard of the swing tower and enable the boom to swing to a fully nested position within the channel space 110, this being the transport position as illustrated in FIGURE 3.

In the operation of the backhoe, normal loading is performed in the usual way. However, the boom 16 may oper-ate more nearly towards a true vertical position to maintain the center of gravity of the backhoe closer to the swing tower and improve the balance and handling characteristics. When the backhoe is finally being swung from the FIGURE 1 position to the FIGURE 3 position, hydraulic pressure is applied to the rod end of the boom cylinders 18 to swing the boom to a true vertical position and then slightly forwardly of vertical as represented in FIGURE 2, wherein the line of action of the boom cylinders 18 registers with the center line of the boom 16. The forward momentum of the parts enables the backhoe to continue through the FIGURE 2 position towards the FIGURE 3 position. Hydraulic pressure is applied at the piston end of the boom cylinders 18 to assist forward travel of the boom from the FIGURE 2 to the FIGURE 3 position. Thereafter, the hydraulic pressure effects a knee lock on the boom to hold the backhoe in the transport position of FIGURE 3.

It may be noted that the swing tower 11 mounts the boom cylinder pivot shafts 17 slightly forwardly of the boom pivot shaft 15 such that in the neutral position of FIGURE 2. wherein the center line of the boom 16 is in registry with the line of action of the boom cylinders 18, i

the boom leans slightly forwardly of true vertical position. This provides more positive control assisting the forward momentum in insuring that the backhoe swings overcenter to enable hydraulic pressure to actuate the boom cylinder in a direction to assist the final forward increment of travel.

To shift the backhoe from the FIGURE 3 position towards the FIGURE 1 position, hydraulic pressure is applied at the rod end of each boom cylinder 18 to initiate rearward swinging movement of the boom. The bucket cylinder is operated at the same time to curl the bucket 26 rearwardly, thereby abruptly shifting the center of gravity to the rear and assisting in the rearward launch of the boom. When the parts move through the FIGURE 2 position, the hydraulic pressure is relieved from the rod end of the boom cylinders.

Thus, while preferred structural features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from .the spirit and scope of the appended claim.

What is claimed is:

1. In a backhoe arrangement, a vertically extending support attachment having vertically spaced mounting portions projecting transversely therefrom and carrying upper and lower pivot means in transversely offset relation from said support attachment for defining parallel upper and lower horizontal axes, said upper pivot means being axially offset relative to said lower pivot means, a boom swingably mounted on said lower pivot means for movement through a neutral intermediate position wherein the boom extends substantially vertically to intersect said upper axis, and double-acting boom cylinder mechanism mounted on said upper pivot means and pivoted to said boom to extend alongside the same and define a line of action in registry with said boom at the neutral position thereof, said double-acting boom cylinder mechanism being extendable to effect swinging movement of the boom and of the cylinder mechanism to either side of said neutral intermediate position.

2. In a backhoe arrangement in accordance with claim 1 and wherein said boom is nested centrally in said support attachment and said boom cylinder mechanism includes a pair of boom cylinders pivoted outboard on said attachment and flanking said boom.

3. In a backhoe arrangement in accordance with claim 1 and wherein said support attachment comprises a cradlelike structure generally U-shaped in plan outline and including a vertical forward wall and a pair of rearwardly projecting sidewalls defining a channel space in which the lower end of the boom is nestable.

4. In a backhoe arrangement in accordance with claim 3 and wherein said sidewalls have lower rearward extremities mounting a boom pivot shaft and upper rearward extremities mounting aligned outboard boom cylinder pivot shafts and said boom cylinder mechanism includes a pair of boom cylinders pivoted on said last named shafts and flanking said boom.

5. In a backhoe arrangement in accordance with claim 4 and wherein the axis of said boom cylinder pivot shafts is slightly forward of said boom pivot shaft and said boom is nestable far enough forwardly into said cradle-like structure to enable extension of said boom cylinder mechanism to effect a knee lock hold of said boom forwardly against said structure to define a positive lock.

6. In a backhoe arrangement, a swing tower comprising a cradle-like structure generally U-shaped in plan outline and including a vertical forward wall and a pair of rearwardly projecting sidewalls defining a channel space, said sidewalls having lower rearward extremities mounting a boom pivot shaft and upper rearward extremities mounting aligned outboard boom cylinder pivot shafts, a boom having its lower end mounted on said boom pivot shaft and nestable in said channel space to be swingable forwardly of true vertical position, and a pair of doubleacting boom cylinders pivoted on said boom cylinder pivot shafts outboard of said tower and flanking said boom and pivoted intermediately on said boom to control swinging movement thereof.

7. In a backhoe arrangement in accordance with claim 6 and wherein the axis of said boom cylinder pivot shafts is slightly forward of said boom pivot shaft and said boom is nestable far enough forwardly into said cradlelike structure to enable extension of said boom cylinders to eifect a knee lock hold of said boom forwardly against said structure to define a positive lock.

References Cited UNITED STATES PATENTS 2,897,986 8/1959 Davis 214-l38 X 3,047,170 7/1962 Hough et al 214138 X 3,244,301 4/1966 Vaughan 214-438 3,282,452 11/1966 Parsen 2 14138 HUGO O. SCHULZ, Primary Examiner. 

